DESCRIPTION: This project will include two subprojects. The first is an ongoing longitudinal normative or of acial sensory aging project (smell, taste, touch, warming and cooling temperature, and pain), and the second will assess sensory changes(touch, warming and cooling temperature, and pain) in the affected dermatomes of patient afflicted with a neuropathic pain condition, postherpetic neuralgia. The normative aging project will assess the effect of aging on sensory functioning (smell, taste, warming and cooling temperature, and pain) utilizing psychophysical assessment methodology in a longitudinal study. Following a baseline neurological examination to screen out individuals with demonstrable neurological deficits, different-aged individuals (four age groups: young (20-29 yrs.), middle (35-44 yrs.), and elderly (65-74 yrs. and >75 yrs.)) will undergo a series of psychophysical studies (threshold and suprathres hold determination for taste, touch, temperature, and pain; and detection and recognition for smell) to assess sensory functioning in the cross-sectional study. The suprathreshold stimuli will be judged in a context of words that describe sensations evoked by these stimuli which: (1) provides a context that will increase the reliability of the suprathreshold sensory judgments, and (2) provides a control for task performance (in the sensory rating paradigm). Measures of suprathreshold sensory discriminability will be determined for each subject and modality. These indices (Pooled Adjacent Violators Algorithm and Kendall's tau) measure both the variability of subject's responses as well as a test for the monotonicity of subject mean rating with increased stimulus magnitude. The data will be analyzed to determine if patterns of sensory change (across modality) exists across different-aged individuals in the cross-sectional analyses. The three-year and (six-year) follow-up neurological examination and sensory assessments will provide longitudinal data to examine the role of time (aging) and/or clinical or sub-clinicalsystemic disease on sensory functioning. Further, in the event that individuals from the sample develop systemic disease with associated neurological deficits (such as stroke) the longitudinal data may provide information about sensory changes that precede the occurrence of these diseases.This latter finding may provide valuable insights into the early diagnosis of potentially debilitating disease, thus potentially allowing for appropriate preventive medical intervention to alter the course of the condition. Further, in the normative aging study, these objective data will be related to self-report measures of oral sensory function obtained from the core questionnaire. The postherpetic neuralgia project will employ the same sensory testing paradigm to assess sensory deficits in older adults afflicted by postherpetic neuralgia. Further, it will assess changes in sensory functioning in individuals being treated for the affliction. This study will provide insights into neuro-mechanisms of neuropathic (non- nociceptive) pain conditions such as post-herpetic neuralgia. For example, pain reduction might coincide with selective return to normal sensory functioning.